/in/foo.c: In function 'main':
/in/foo.c:22:2: error: 'k' undeclared (first use in this function)
  k = Search(a, n, x);
  ^
/in/foo.c:22:2: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:26:10: warning: too many arguments for format [-Wformat-extra-args]
   printf("No Exist\n",x);
          ^~~~~~~~~~~~